Fuel burner



Jan. 7, 1941. G. GRUBB 2,227,899

' FUEL BURNER Filed Oct. 8, 1936' 2 SheetsSheet 1 ilill lNvvEN 20R 'iIQMu/M A; ATTORNEY Jan. 7, 1941. I GRUBB 2,227,899

I FUEL BURNER Filed OCt. 8, 1936 2 Sheets-Sheet 2 INVENTOR j&mwdm ja BYMATTORNEY Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE FUEL BURNERApplication October 8, 1936, Serial No. 194,584 In Germany December 11,1935 11 Claims.

My invention relates to the art of fuel burners.

In liquid fuel burners, particularly of the distillate type, the liquidfuel, such as kerosene, is caused to be heated and vaporized. Thevaporized fuel is mixed with air to provide a combustible mixture. Theamount of heat produced by the burner is dependent upon the rate ofvaporization of the fuel which is most readily controlled by regulatingthe flow of liquid fuel to the burner. It is usually difficult tocontrol the burner flame in this manner in any reasonable length of timewithout disturbing the operation of the burner. Thus, when it is desiredto increase the size of the burner flame by increasing the rate of flowof liquid fuel, for example, a too rapid flow of liquid fuel often takesplace which produces objectionable vapor flashes in the burner. Further,in many gas burners, the admission of an adequate quantity of air toinsure complete combustion of the fuel tends to increase the likelihoodof back-firing of the burner.

It is an object of my invention to provide an improved liquid or gaseousfuel burner in which the admission of an adequate quantity of air is 25insured to provide a flame which is odorless and substantially free fromsmoke and soot.

Another object of my invention is to provide an improved liquid orgaseous fuel burner which permits the admission of an adequate quantityof 30 air to insure substantially complete combustion of the fuel andyet avoids the danger of backfiring of the burner.

A further object of my invention is to provide an improved burner whichmay be operated with liquid fuel and in which nice control of the burnerflame is obtained.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the claims. The invention itself, 40however, both as to organization and method,

together with further objects and advantages thereof, will be betterunderstood by reference to the following description taken in connectionwith the accompanying drawings of which Fig. 1 diagrammaticallyillustrates a burner embodying my invention shown in connection with aliquid fuel supply system; Fig. 2 is a vertical sectional view of theburner shown in Fig. l; and Figs. 3 to 6 inclusive are verticalsectional views illustrating modifications of the burner shown in Fig.2.

Referring to Fig. 1 of the drawings I have shown my invention inconnection with a liquid fuel supply system of the pressure type. It isto be understood, however, that my'invention can be employed with othertypes of liquid fuel supply systems and operated with gaseous as well asliquid fuel. The liquid fuel supply system includes a supply vessel [0from which fuel is conducted through a conduit II to a burner l4. Theburner I4 is at a higher level than the liquid fuel in the supply vessell0 and liquid fuel is caused to flow to the burner [4 by maintaining theliquid fuel under pressure in the supply vessel l0. This may beaccomplished by providing 1 the supply vessel [0 with an air-tightfilling cap l5 and connecting the upper part of the supply vessel bymeans of a conduit l6, control valve l2, conduit l1, control valve l8,conduit l9, storage vessel 20 and conduit 2| to the cylinder.22 of an 1air pump 23. Within the cylinder 22 is arranged a piston 24 to which isconnected a piston rod 25 which extends through an opening at the end ofthe cylinder and serves as a handle for the air pump. When the rod 25 ismoved inward 20 valve 28 is provided adjacent the air pump 23 to preventair from flowing from the conduit 2| to the cylinder 22.

In order to stop the flow of liquid fuel to the burner I4 when theburner flame is extinguished, I provide the control valve l2 which isarranged to be responsive to the temperature of the burner flame. Thecontrol valve l2 comprises a cylindrical shaped casing 29 within whichis accurately fitted a cylindrical shaped valve member. 30 of smallerdiameter than the casing 26. The valve member 30 is secured to a rod 3lwhich extends througli an opening in the casing and is connected to anexpansible bellows 32. The bellows 32 is connected by means of atube 33to a thermal bulb 34 arranged adjacent to the burner It. The bellows 32;tube 33, and thermal bulb 3E constitute what is termed an expansiblefluid thermostat-which is filled with a suitable volatile fluid whichincreases and decreases in volume with corresponding changes oftemperature.

When the burner l lis being operated the volatile fluid in theexpansible bellows 32 increases in volume and the valve 30 is in theposition shown in Fig. 1. In this position the passage 35 ment of thevalve 39, the conduits l1 and I9 are of the valve 30 communicates withthe conduits I6 and H and the supply vessel i0 is in open communicationwith the storage vessel 29, so that the fuel in the supply vessel ismaintained under pressure. If for any reason the burner flame isextinguished, the expansible bellows 32 contracts and the valve 30 ismoved toward the left, and, when the vertical portion of the passage 35is moved adjacent to the opening 31 in the casing 29, the air underpressure in the supply vessel I6 is discharged to the atmosphere to stopthe flow of fuel to the burner.

. A second control valve l8 may be connected to the conduits l1 and I8for automatically controlling the operation of the burner 4. The controlvalve I8 includes a cylindrical shaped casing 38 within which isaccurately fitted a cylindrical shaped valve member 39 of smallerdiameter than the casing 38. The valve member 39 is secured to a rod 40which extends through an opening in the casing and is connected to anexpansible bellows 4|. The bellows 4| is connected by means of a tube 42to a thermal bulb 43 which is arranged to be responsive to a temperaturecondition affected by a part of apparatus, diagrammatically indicated at44, which is adapted to be influenced by the operation of the burner.The bellows 4|, tube 42, and bulb 43 also constitute an expansible fluidthermostat which may be filled with a suitable volatile fluid whichincreases and decreases in volume with corresponding changes oftemperature. When the part 44 of the apparatus tends to fall below adesired temperature, the volatile fluid becomes reduced in volume andcauses the expansible bellows 4| to contract and move the valve member39 to the position shown in Fig. 1. In this position the passage 45 inthe valve 39 communicates with the conduits l1 and I9 and liquid fuel inthe supply vessel is maintained under pressure and will flow to theburner When the part 44 of the apparatus tends to rise above the desiredtemperature, the increase in volume of the volatile fluid causes theexpansible bellows 4| to expand and move the valve member 39 toward theright. With such moveblocked to disconnect the storage vessel 20 fromthe fuel supply vessel I0; and, as the passage 45 in the valve 39 movesadjacent to the opening 46 of the casing 38, the air in the supplyvessel I9 is permitted to discharge into the atmosphere whereby thepressure therein is gradually released so that fuel is no longer causedto flow to the burner l4.

Thecontrol valve l8 and expansible fluid thermostat associated therewithare preferably so arranged that, when the part 44 of the apparatus issubstantiallyat the desired temperature, the valve 39 assumes such aposition that the vertical portion of passage 45 is between theconnection of the casing 38 to the conduit l9 and the opening 46,whereby the storage vessel 26 is blocked off without completely reducingthe pressure in the supply vessel l0. With the storage vessel 28 blockedoff the pressure in the supply vessel I0 gradually becomes smaller asliquid fuel flows to the burner 4 with the result that the burner flamebecomes reduced in size. The reduction in size of the burner flamedecreases the amount of heating effected by the burner and avoidscompletely shutting off the supply of liquid fuel to the burner |4. Onlywhen the part 44 of the apparatus rises above the predeterminedtemperature is the valve 39 moved toward the right such a distance thatthe passage 45 communicates with the opening 46, whereby the pressure inthe supply vessel I0 is released and the flow of liquid fuel to theburner I4 is stopped.

In accordance with my invention the burner I4 includes a metallic shell41 within which is arranged a body 48 of porous material ofsubstantially the same cross-sectional area as the shell. The body orplate 48 of porous material is spaced from the conical shaped bottom ofthe shell to provide a chamber 49 into which the liquid fuel dischargesfrom conduit Above the plate 48 is provided a second body 50 of porousmaterial which extends to the top of the shell 41 at which region theburner flame is maintained. A perforated cover plate 5| is secured inany suitable manner to the top of the shell 41.

A sleeve 52 depends downward from the bottom of the shell 41 andcommunicates with a small vessel 53 which is connected by a verticalconduit 54 to the chamber 49 of the shell 41. A tubular member 55extends downward from the cover plate 5| through the bodies 50 and 48 ofporous material and sleeve 52 into the vessel 53,. Within the tubularmember 55 is disposed a wick 56 which provides a small ignition flame atthe top perforated cover 5| of the burner.

A group of conduits 51, only one of which is shown, extend upward fromthe bottom of the shell 41 and terminate in the interior of the body 50of the porous material. A second group of conduits 58, only one of whichis shown, extend upward from the bottom of the shell 41 through thebodies 48 and 50 of porous material and at their upper ends aresubstantially flush with the perforated cover plate 5|.

When the burner is being operated, the chamber 49 and small vessel 53are filled with a liquid fuel, such as kerosene, which is underpressure. The wick 56 fits tightly within the tubular member 55 wherebyliquid fuel is prevented from freely flowing upward through the tubularmember 52. The body 48' of porous material preferably is formed of amaterial, such as calcined or burned clay, pressed asbestos, porouscoal, or any other suitable fibrous organic material, for example, whichis capable of causing distribution of fuel therein. The body 48 offers acertain resistance to the flow of liquid fuel therethrough, and, inaddition to bringing about a distribution of the fuel, also serves toreduce or lower the pressure of the fuel due to the pressure drop whichtakes place therein. which fuel reaches the body 50 of porous materialat a given pressure of the liquid fuel in the chamber 49, therefore, islargely dependent upon the pressure drop of the fuel in the body 48 ofporous material.

The body 56 of porous material preferably consists of a material, suchas the oxides of calcium, strontium or barium, sandstone, or charcoal orthe like, for example, which is in the form of grains or granules andcapable of bringing about a distribution of the liquid fuel. Thematerial forming the body 50 may be slightly compressed and possessessuch physical properties that the liquid fuel is distributed uniformlyin the body by capillary forces. The density or porosity of the body 50as well as the size thereof relative, to the quantity of fuel passingtherethrough are preferably so chosen that the material is neversaturated with liquid fuel.

Due to the relatively large surface presented by the grains 0r granulesof material forming The rate at the body 50, the liquid fuel evaporatesat a relatively high rate in this body. In the particular embodimentshown in Fig. 2, a relatively high evaporation of the liquid fuel in thebody is assured by the provision of conduits 51 for admitting air withinthe body. In this manner a sufficient quantity of air can be mixed withvaporized fuel to provide a combustible gas mixture even before the fuelreaches the cover plate 5| at which region the burner flame ismaintained. Due to the suction action of the burner flame, the admissionof air through the conduits 51 into the body 50 of porous material isfacilitated. The suction action of the burner flame is also effectivelyutilized for drawing additional air through the conduits 58 into theregion of the flame to insure complete combusion of the fuel. When theburner is being operated, the top part of the body 50 of porous materialis heated above the evaporating temperature of the fuel and in thismanner accelerates the evaporation of fuel in the upper layer ofmaterial.

When the expansible fluid thermostat associated with the control valvel8 becomes operative to move the valve member 39 toward the right topermit the air in the supply vessel Hi to discharge into the atmosphere,the level of the liquid fuel in the vertical'po-rtion of the conduit His lowered and air is drawn downward through the bodies 50 and 48 ofporous material. In this manner vaporized and liquid fuel is drawn offthe bodies of porous material whereby a continued odorless burning ofthe ignition flame is, insured. The likelihood of odors being producedwhen the main flame of the burner I4 is extinguished is not very greatwhen substances such as charcoal are used, inasmuch as such substancesare capable of adsorbing odors in relatively large quantities.

Fig. 3 illustrates a modification of the embodiment just described anddiffers therefrom in that the porous body 480. is so arranged that airis permitted 1 to pass therethrough. The burner shown in Fig. 3 includesa cylindrical casing 41a which may be provided with legs or supports 59.

Within the casing 41a are arranged the bodies 48a. and 50a. of porousmaterial which are similar to the bodies 48 and 50 shown in Fig. 2. Tothe casing at the lower surface of the body 48a is secured a protectiveperforated sheet of material 60, such as a wire screen. A plurality ofconduits 6| extend vertically upward through the bodies 48a and 58a.from the bottom surface of the body 48a to the perforated cover plate5Ia arranged at the top of the casing 610,.

About the casing 41a adjacent to the body 48a is tightly fitted a hollowannular shell 62 which is connected by means of a conduit I la to thesource of fuel supply. The casing 41a and the inner wall of the shell 62are provided with a plurality of aligned openings, as indicated at 63,for admitting fuel to the interior of the body 48a of porous material.

When the burner is being operated, air is drawn upward through theconduits 6| into the region of the burner flame to insure completecombustion of the fuel. Since the lower surface of the body 43a isexposed to the atmosphere, air is drawn into this porous mass at itslower surface due to the suction action of the burner flame, as in theembodiment shown in Fig. 2, and passes upward therethrough into the body50a. The fuel introduced into the body 48a through the openings 63passes upward into the body 50a in which it isvaporized and mixes withair entering through the body 48a to provide a combustible mixture. Inthis modification, as in the embodiment described above, the density ofthe body 50a as well as the size thereof relative to the quantity offuel passing therethrough, are chosen so that the material is neversaturated with liquid fuel. Preferably the pressure of the liquidfuelsupplied to the burner is adjusted so that, in the event the burnerflame is extinguished, the pressure of the liquid fuel in the portion ofthe body 48a near the lower surface, which is exposed to the atmosphere,is sufliciently small to insure the adherence of liquid fuel within thebody due tothe capillary action of the porous material.

My invention may assume many different forms. -It is possible and, inview ofthe varying properties of different fuels, it is even necessaryand desirable to make various changes in practicing the invention. Whenoperating with liquid fuel, such as kerosene, for example, it isnecessary to take into consideration the properties of the fuel, such asits volatility and flash point, and accordingly determine the size anddensity of the upper porous body which effects distribution andevaporation of the fuel and the size and density of the lower porousbody which serves to reduce the pressure of the fuel.

When liquid fuel of relatively low volatility is used, for example, thelower body of porous material may be used alone and thereby serve as anevaporator body as well as effect distribution of the fuel. Such amodification is shown in Fig. 4 in which parts similar to those shown inFig. 3 are designated by the same reference numerals.

' In Fig. 4 the body 480. extends upward to the top such aflinity themore actively is the oxygen released. Among the catalysts which may beused for this purpose are the peroxides of the alkaline earth metals,especially of barium, and the higher oxides of manganese, iron, andchromium. It is not necessary that the fuel itself absorb the oxygenfrom the material employed as a catalyst because so-called activatedoxygen which is released from such materials may unite chemically withthe fuel in the burner flame.

In the embodiment shown in Fig. 2, for example, catalysts of thecharacter just described may be added to the body 50 of porous materialor used as the upper porous body above the plate 48. It is particularlydesirable in many instances to use such catalysts to form the upperlayer of 2 in that it ismodified for gas operation with the.

conduit II and central tubular member 55' adapted to be connected to asuitable source of supply of gaseous fuel. A valve 64 may be provided inthe conduit I I to control the pressure of the gas delivered to thechamber 49. The tubular member 55' permits the flow of a small quantityof gas to provide an ignition or pilot flame for starting the burner.Above the body 50 of porous material is provided an upper layer 65 ofmaterial adapted to serve as a catalyst whereby a socalledauto-oxidation of the fuel-is effected or activated oxygen is produced,as described above.

Such a layer of material may be also used when the burner is adapted tobe operated with a suitable liquid fuel, such as kerosene.

In many instances it is possible to employ a burner adapted to beoperated with liquid fuel wherein only the upper porous body formed ofgrains or granules is used. With such burners, as shown in Fig. 6, thebody 50 of porous material may be of the same cross-sectional area asthe casing 41. In the modification shown in Fig. 6, the small supplyvessel 53 is omitted although it may be provided in a manner similar tothat shown in Fig. 2. The body 50 of porous material may be supported ona sheet of perforated material 66, such as a wire screen, which isspaced from the bottom of the casing 41 to provide the chamber 49 intowhich the fuel discharges from the conduit ll. When a relatively smallflame is desired, difficulty has usually been encountered in liquid fuelburners to adjust and maintain a low rate of flow of fuel to the burner.In accordance with my invention the path of flow of fuel in the burnerneed not be made small to produce a small flame and it is only necessaryto adjust the air pressure under which the fuel is maintained at thesupply vessel or the elevation of the supply vessel with respect to theburner where grav ity feed of fuel is employed.

In instances where a relatively volatile liquid fuel is employed thereis always present in the upper layer of the porous body practically acombustible gaseous mixture. If desired, therefore, the top of theburner may be connected by a suitable conduit to a nozzle or burner ofthe Bunsen type.

A burner of the character shown in Fig. 6 may be operated with a gaseousfuel, particularly when the gas pressures are not too high. A gasmixture rich in air can easily be obtained by the provision of conduits51 and 58 for drawing air into the interior of the body 50 and to thetop of the burner due to the suction action of the flame. If desired,the conduits 58 may be provided with a plurality of spaced openings 61along their length within the body 50.

The conduits 58 may also be effectively used to conduct heat from theregion of the burner flame into .the body or bodies of porous material.If it is desired to increase the evaporation of fuel in the body ofporous material by the heating efi'ect of the burner flame, rods orconduits 68, one of which is indicated in Fig. 6, may be provided, suchrods extending from a point above the top cover plate 5| downward intothe body of porous material. The use of such rods is particularlydesirable when fuel of relatively low volatility is used.

In view of the foregoing, it will be understood that I have provided aburner which insures substantially complete combustion of thefueil andyet avoids danger of back-firing. The burner is especially useful wherecontinuous operation is desired, such as for refrigeration apparatus orhot water heaters,-withoutthe necessity of frequent servicing. Further,the burner structure is such that a simple automatic control thereformay be provided even when operated with liquid fuel. Although I haveshown and described several embodiments of my invention, such variationsand modifications are contemplated as fall within the true spirit andscope'of my invention, as pointed out in the following claims.

What is claimed is:

1. A burner including a casing, a body of porous material arrangedwithin said casing and through which liquid or gaseous fuel is adaptedto flow, said body being capable of causing distribution of the fueltherein, a layer of material contiguous to said body within said casingand at the outer surface of which the flame is maintained, means topermit air to be drawn into the interior of said body by the suctionaction of the flame to form a combustible mixture with the distributedfuel, and said layer of material being capable of absorbing oxygen fromthe air and releasing such oxygen at a higher temperature to the fuel.

2. A burner including a casing, a body of porous material arrangedwithin said casing, said body being capable of causing distribution offuel therein, the flame being maintained at one surface of said body,means to permit air to be drawn into the interior of said body by thesuction action of the flame to form a combustible mixture with thedistributed fuel, and the layer of said body adjacent the outer surfaceat which the flame is maintained including a substance which is capableof absorbing oxygen from the air and releasing such oxygen at a highertemperature to the fuel.

3. A burner including a casing and a body of porous material therein andat the upper surface of which the burner flame is produced andmaintained, means to conduct and supply liquid fuel to the lower surfaceof said body to cause flow of fuel therethrough, a chamber adapted toreceive liquid fuel conducted to said body, a wick extending from saidchamber to the upper surface of said body to provide an ignition flame,and said chamber being constructed and arranged to receive and hold aquantity of liquid fuel even when the supply of fuel to said body isshut oil.

4. A burner including a casing and a body of porous material therein andat the upper surface of which the burner flame is produced andmaintamed, means to conduct and supply liquid fuel under pressure to thelower surface of said body to cause flow of fuel therethrough, a tubeextending vertically through said body and terminating at the .uppersurface thereof, a wick in said tube extending into liquid fuel underpressure to provide an ignition flame at said upper surface, and saidwick fitting tightly in said tube to prevent free flow of liquid fueltherethrough.

5. A burner including a casing and two bodies of porous materialdisposed therein one above the other and contiguous to each other, theupper body being of greater porosity with the burner flame beingproduced and maintained at the upper surface thereof, means to conductand supply fuel to the lowerbody and cause flow of fuel successivelythroughsaid lower and upper bodies, one or more hollow members extendinginto the interior of said upper body and through which air is drawnbythe suction action of the flame, and one or more additional hollowmembers extending through said upper body and terminating at the uppersurface thereof and through which air is drawn into the region of theflame by the suction action thereof.

6. A burner including a casing and a body of porous material disposedtherein and at the upper surface of which the burner flame is producedand maintained, means to conduct and supply fuel to the lower surface ofsaid body to cause flow of fuel therethrough, one or more hollow membersextending into the interior of said body and through which air is drawnby the suction action of the flame, and one or more additional membersfuel and the second body being of such porosity extending through saidbody and terminating at the upper surface thereof and through which airis drawn into the region of the flame by the suction action thereof. 4

7. A burner including a casing and a body of porous material disposedtherein and at the upper surface of which the burner flame is producedand maintained, means including a chamber below said body of porousmaterial to conduct liquid or gaseous fuel to the lower surface of saidbody to cause upward flow of fuel therethrough to said upper surface,and one or more hollow members extending through said chamber into theinterior of said body and through which air is drawn by the suctionaction of the flame to cause the air to flow in the same direction asthe fuel in said body.

8. A burner including two bodies of porous material of which theporosity of one is greater than that of the other, the burner flamebeing produced and maintained at a surface of said body of greaterporosity, means to cause flow of fuel successively through said bodieswith the fuel passing first through said body of least porosity, and aregion within said body of greater porosity being in communication withsurrounding air whereby air can flow into the interior of said body andmix with fuel therein.

9. A burner including a first body of porous material and a second bodyof porous material at a surface of which the burner flame is producedand maintained, means to conduct fuel under pressure to said first bodyto cause flow of fuel successively through said first and second bodies,the burner being so constructed and arranged that air will flow into theinterior of said second body and mix with fuel distributed therein, andsaid first body being of such porosity that it is primarily effective toreduce the pressure of the that it is primarily capable of causingdistribution of the fuel therein by capillary action.

10. A burner including a casing and a body of porous material disposedtherein and at the upper surface of which the burner flame is producedand maintained, means including said casing providing a chamber at theupper boundary of which is disposed substantially all of the lowersurface of said body of porous material, means including a conduitconnected to said chamber for causing flow of fuel through said body,said body being capable of causing distribution of fuel therein with thefuel entering said body from said chamber substantially uniformly at thelower surface thereof, and means extending from a point above saidsurface into the interior of said body for transmitting heat from theflame to fuel within the body.

11. A burner including a body of porous material and a second body ofmaterial of greater porosity at the surface of which the burner flame isproduced and maintained, means forming a chamber adjacent to said firstbody and at least as great in lateral extent as said first body, saidchamber being formed and arranged to provide communication between saidchamber and a plurality of portions of the peripheral area of said firstbody, means including a conduit connected to said chamber to conductfuel under pressure to said chamber and to cause flow of fuel therefromsuccessively through said first and second bodies during operation ofthe burner, said first body of least porosity possessing such physicalproperties that it is primarily eifective to reduce the pressure of theflow of the fuel, and the second body of greater porosity possessingsuch physical properties that it is primarily capable of causingdistribution of the fuel therein by capillary action.

GUNNAR GRUIBB.

